A seatbelt assembly conventionally equipped in a vehicle such as an automobile is designed to bind the occupant with the seatbelt in the emergency case, to prevent the occupant from being thrown out of the seat.
Such a seatbelt assembly includes a seatbelt retractor that retracts the seatbelt. In the seatbelt retractor, the seatbelt is wound around a spool when not in use, and withdrawn to be worn by the occupant when in use. In an emergency case as cited above, a locking device of the seatbelt retractor is activated so as to restrict the spool from rotating in the direction to withdraw the belt, thereby restricting the withdrawal of the seatbelt. Thus, the seatbelt binds the occupant in the emergency case.
In relation to the seatbelt retractor of the conventional seatbelt assembly, when the seatbelt binds the occupant in an emergency case such as vehicle collision, large vehicle deceleration is generated and hence the occupant is urged to move forward by large inertia. Accordingly, the seatbelt is subjected to a large load and the occupant is subjected to a large amount of energy from the seatbelt. Although such energy is not a critical issue to the occupant, it is preferable that the energy is limited.
Therefore, conventionally a torsion bar is provided in the seatbelt retractor, so as to limit the load applied to the seatbelt in an emergency case that happens while the seatbelt is worn by the occupant, thus to absorb and alleviate the energy.
However, in the conventional seatbelt retractors only a single load limit is specified with respect to a case of collision. Actually, the energy imposed on the occupant varies depending, for example, on the body weight of the occupant. Therefore, setting different load limits, instead of just one, in accordance with the situation of the emergency case to cope with the large energy that varies depending on the situation allows the occupant to be bound more effectively and more properly.
Accordingly, seatbelt retractors that allows setting of various limits to the load applied to the seatbelt have been proposed (see, for example, PTL 1).
The seatbelt retractor according to PTL 1 includes a pair of EA mechanisms having different EA characteristics, and one or both of the EA mechanisms are activated depending on the situation of the emergency case. Selectively activating the pair of EA mechanisms allows the load limit on the seatbelt to be set in two stages, depending on the situation of the emergency case.